In an MFPB antenna with multiple radiofrequency RF feeds per beam, each beam is formed by combining the ports of multiple radiofrequency feeds of a focal array, each radiofrequency feed being composed of a radiating element connected to a transmission and reception radiofrequency chain that generally has two ports. For this purpose, the RF feeds of the focal array are grouped into a plurality of elementary cells comprising the same number of RF feeds and forming a mesh. According to the placement of the radiofrequency feeds in the focal array and the number of radiofrequency feeds in each mesh cell, the mesh cell may have various geometric forms, square or hexagonal for example. The ports of the radiofrequency feeds of each mesh cell may then be mutually combined in order to form a beam. In order to obtain a good overlap of the beams, it is known practice to reuse one or more radiofrequency feeds to form adjacent beams. The reuse of the radiofrequency feeds is generally implemented in two spatial dimensions, which conventionally requires the use of a complex beam forming network BFN comprising axially positioned power combiner circuits that criss-cross each other, and it is then impossible to physically separate the combiner circuits dedicated to the formation of different beams. This difficulty is compounded by the use of shared couplers with multiple radiofrequency feeds, which allow the radiofrequency feeds to be reused and the mutual independence of the beams. It is therefore not possible to construct and assemble these antennas in a modular form and the number of beams that may be formed is limited.
The document FR 2 939 971 describes an especially compact radiofrequency feed comprising an RF chain with four ports, two of which are transmission ports respectively operating in two polarizations P1, P2 that are orthogonal to one another and two of which are reception ports respectively operating in the two polarizations P1 and P2. The transmission ports and the reception ports respectively operate in two different frequency bands F1 and F2. This radiofrequency feed comprising four independent ports allows two independent beams to be formed on transmission and on reception.
The document FR 2 993 716 describes an architecture for an MFPB transmission and reception antenna comprising a focal array equipped with compact radiofrequency feeds with four ports, in which each beam is produced by a group of four radiofrequency feeds of the array, by combining in fours the ports with the same polarization and the same frequency of each of the four radiofrequency feeds. This antenna operates in transmission and in reception, and two adjacent beams operating in orthogonal polarizations are produced by two different groups of RF feeds, each composed of four radiofrequency feeds that are able to share one or two radiofrequency feeds according to the arrangement of the four RF feeds in the mesh cell. This architecture allows the radiofrequency feeds to be reused only in a single spatial dimension and requires the use of a second, identical antenna in order to obtain a good overlap of the beams in both spatial dimensions. This antenna architecture is therefore particularly simple as two adjacent beams are implemented by combinations of different ports, thereby allowing the use of independent BFNs, each BFN comprising combination circuits dedicated to the formation of a single beam. However, this document gives no information on a possibility of constructing the focal array of the antenna in a modular form, nor on the possibility of assembling the feeds and the BFNs without the components of the various BFNs overlapping.